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January 8, 2019 -- Led by significant growth in the use of CT, the utilization of noncardiac chest imaging increased markedly in the emergency department (ED) during the past few decades, according to research from the Harvey L. Neiman Health Policy Institute published online January 2 in the Journal of the American College of Radiology.

The Neiman researchers, led by Dr. Joseph Chung of the University of Chicago, evaluated national and state-level Medicare data from the U.S. Centers for Medicare and Medicaid Services (CMS) for 1994 to 2015. They found that chest radiography utilization increased at a compound annual growth rate (CAGR) of nearly 5% during the study period, while CT climbed at a CAGR of over 20%.

"This [increase in ED utilization of chest imaging] was related not only to an increasing frequency of ED visits but also to increasing utilization per ED visit," senior author Dr. Andrew Rosenkrantz of NYU Langone Health said in a Neiman statement. "Across states, utilization is highly variable, but with radiography and CT both increasing, the use of CT seems additive to, rather than replacing, radiography."

The researchers reviewed the aggregate 100% Medicare Physician/Supplier Procedure Summary Master Files for 1994 to 2015 to determine the annual frequency of ED chest radiography, CT, and ultrasound performed on Medicare Part B beneficiaries nationwide. Utilization rates were normalized to annual Medicare enrollment, as well as to the number of annual ED visits, according to the researchers. Next, they analyzed the CMS 5% research-identifiable files to determine service-level volumes for each state for 2004 and 2015.

Increase in noncardiac emergency chest imaging from 1994-2015 in the U.S.

Chest radiography

CT

Per 1,000 Medicare beneficiaries

171% (CAGR, 4.9%)

5,941.8% (CAGR, 21.6%)

Per 1,000 Medicare beneficiary ED visits

81% (CAGR, 2.9%)

3,915.4% (CAGR, 19.2%)

On a statewide basis, radiography utilization per 1,000 ED visits in 2015 ranged from a low of 82 in Wyoming to a high of 731 in Hawaii. Wyoming also had the lowest utilization rate of CT (18 per 1,000 ED visits), while Hawaii had the highest CT utilization -- 76 per 1,000 ED visits.

Most states demonstrated higher utilization of both radiography and CT between 2014 and 2015, according to the researchers. Vermont had the highest CAGR in radiography at 11%, and Maine had the highest CAGR for CT at 21%.

"Longitudinal state-by-state data revealed considerable heterogeneity in the extent of state-level increases of the use of thoracic imaging in the ED setting," Chung said in a statement. "Despite this heterogeneity, nearly all individual states showed increased utilization over time for both ED thoracic radiology and CT."

Six states -- West Virginia, Maine, Hawaii, North Dakota, South Dakota, and Vermont -- were among the top 10 for highest growth in utilization for both radiography and CT, according to the researchers. They did note, however, that the rate of radiography dipped in four states and the rate of CT dropped in one state.